Computational fluid dynamic analysis on tribological performance under hydrodynamic lubrication of dimple textured surface produced using turning process

Abstract

It is known that the functional performance of a surface can be improved by introducing a dimple structure. Dimple structured surface has stunningly benefited tribological performance in many ways, such as in reducing friction and increasing load capacity. This paper presents an analysis of coefficient of friction (COF) and load capacity using computational fluid dynamics (CFD) for various dimple sizes, shapes, depths and area ratio which are able to be fabricated using a turning process with a carbide insert grade H1 with the aid of dynamic assisted tooling turning (DATT) on a hypereutectic aluminium silicon alloy (A390). The said material is commonly used for piston components in automotive application. Dimples of short drops and long drops can be produced in the range of length of 517.03–3927.61 μm; width of 565.15–1039.19 μm; depth of 14.46–124.87 μm; and area ratio of 5.05–25.65%. Dimple shape with the area ratio of 10–20% has the ability to increase load capacity and reduce COF. The CFD results indicated that a low COF of 0.29 was obtained with dimensionless load capacity of 0.08486, dimensionless shear force of 0.025 and more positive pressure distribution along the sliding direction with the dimple structure of 829.22 μm in width, 1026.65 μm in length, 110.70 μm in depth and area ratio of 12.70%. Load capacity was influenced by the depth and width of the dimple produced and positive pressure distribution at the liner wall. The untextured surface had a high COF of 39.29 because pressure generation could not be generated due to the absence of dimples on the surface. This revealed that the presence of dimple on a surface helps to improve the pressure generation for increased load capacity. The huge gap difference of COF between untextured surface and dimpled surface of 39 proved that the presence of dimples contributes to the reduction of friction. Therefore, if properly applied, dimple structured on the surface of the piston skirt could significantly reduce fuel consumption due to its ability to reduce friction and therefore could prolong the service life of the related engine components.